I had to enable quota support to my hard disk mounts on one of my new Plesk boxes today. This lets Plesk manage how much space is given to whomever… very necessary for a virtual hosting box.

I found these instructions on the Plesk forum, but not all in one place, hence…

Add ‘usrquota’ to the options in fstab. Mine looked like this before and after…
before
/dev/md0 / ext3 defaults 1 1

after
/dev/md0 / ext3 defaults,usrquota 1 1

Then run these to get quotas working…
# mount -o remount /
# quotaoff -av
# quotacheck -avum
# quotaon -av

..and that should be you good to go.